Chimpanzees are fans of alcoholic plant sap in wild. Who knew?

Chimpanzees have shown us over time that they have an understanding of language and exhibit a sense of fairness, but now researchers have discovered that our closest primate kin also like to have a good, stiff drink every now and again.

As part of a 17-year study, scientists in Guinea have collected evidence of long-term and repeated imbibing of ethanol alcohol by chimps. Remarkably, the chimps use chewed up leaves as a sort of "cup" to drink, BBC News reports. Some of them even drank enough that they were visibly drunk.

People living in the Bossou area of Guinea, where the research was conducted, like to harvest "palm wine" from these trees, and they do this by tapping them at the crown and gathering the sap in plastic containers. They collect the sap in the mornings and evenings. Then the chimps like to collect some of the sap from the containers.

Crushing and chewing on leaves, the chimps used these as sponges so that they could dip into the liquid and suck out the contents.

The scientists also charted how the apes drank, and found that just like humans, there were boozers and teetotalers, Gizmodo reports.

"Individuals either co-drank, with drinkers alternating dips of their leaf-sponges into the fermented palm sap, or one individual monopolized the container, while others waited their turn. Thirteen of 26 adult and immature individuals present in the Bossou community between 1995 and 2012 (excluding infants) were never seen ingesting palm sap," the researchers noted in the report.

Conducting tests on raffia palm sap also showed that the alcohol content of the drink varied throughout the day, as the sugars increased and fermented the alcohol. On average, the liquid contained 3.1 percent alcohol by volume (ABV), more or less the same as some beers, The Guardian reports. The strongest sap tested at about 6.9 percent ABV.

The drink was equally popular with males and females, but on an individual level, the apes varied in how much they drank.

"Some individuals were estimated to have consumed about 85ml of alcohol, the equivalent to about 8.5 UK units [about the same as a bottle of wine]" Dr. Kimberley Hockings from Oxford Brookes University and the Centre for Research in Anthroplogy in Portugal, told BBC News.

"On another occasion after drinking palm wine, one adult male chimpanzee seemed particularly restless," she said. "While other chimpanzees were making and settling into their night nests, he spent an additional hour moving from tree to tree in an agitated manner. Again pure speculation, but it's certainly something we would like to collect further data on in the future."

Over the years, there have been unconfirmed anecdotes about non-human primates consuming alcohol in the wild, however, this is the first time that researchers have recorded and measured wild apes voluntarily imbibing alcohol.

That the chimps and humans alike fancy alcohol add another facet to the story of our shared evolution. A recent study by Matthew Carrigan, of Santa Fe College in the U.S. shows that humans and African apes share the same genetic mutation that enables them — and us — to effectively metabolize ethanol.

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It's the evolutionary origin of this gene that may have "opened access to good energy sources — all that simple sugar — that were accidentally 'protected by noxious alcohol," said Professor Richard Byrne, an evolutionary biologist from the University of St. Andrews.

"And presumably, whatever its evolutionary origin, it is that adaptation which makes me able to enjoy a good malt."

So the next time you quaff a beer, why not raise a toast for the chimps?